1. Field of the Invention
The present invention relates to a method of fabricating ohmic contact on n-type gallium nitride (GaN) of room temperature by plasma surface treatment.
2. Discussion of the Related Art
Metal contact is one of the most important processes in fabricating opto-electronic devices and high-temperature, high power electronic devices using gallium nitride (GaN)—based compound semiconductors. In particular, ohmic metal contacts with low specific contact resistivity are essential to obtain high performance devices. The ohmic contact is strongly dependent on the interfacial property between metal contacts and the semiconductors. Despite numerous attempts to improve metal contact property, it has been very difficult to fabricate GaN devices with low contact resistivity using the conventional techniques involving Si and GaAs since the work function of the GaN is much higher than the other semiconductor materials.
Obtaining a low ohmic contact having a resistivity less than 10−6 ohmcm2 by Ti/Al ohmic contact, which is widely used to form n-type ohmic contact on GaN, has been only possible by heat treatment higher than 600 C (see FIG. 1). However, such a high temperature process results in not only limiting the process design for device fabrication but also degrading the device performance. Therefore, a non-alloy heat treatment technique that can be used to obtain a low contact resistivity from the as-deposited metal contact would exhibit substantial advantages in reducing the cost of the fabrication process and improving the device reliability.